Assembling apparatus and assembling method

ABSTRACT

An assembling apparatus places a retainer on a valve spring to surround an upper end of a valve stem. The apparatus includes an assembling head, and a moving unit configured to move the assembling head between the supply position of the retainer and an assembling position. The assembling head includes a holding unit configured to hold the retainer, and a push unit configured to push out the retainer. The push unit includes a push member supported to be able to advance/retreat along an elevating direction of the assembling head, and a biasing member configured to bias the push member in an advancing direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/802,222 filed on Nov. 2, 2017, which is a continuation ofInternational Patent Application No. PCT/JP2015/080078 filed on Oct. 26,2015, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a technique of assembling a retainer tothe valve stem of an engine.

BACKGROUND ART

A retainer is attached to a valve stem via a pair of cotter pieces. Thepair of cotter pieces are parts that engage with the valve stem.Japanese Patent Laid-Open No. 10-61420, Japanese Patent No. 4033703 andJapanese Patent Laid-Open No. 2012-241519 each disclose an apparatus forassembling a retainer with a pair of already assembled cotter pieces toa valve stem. An apparatus of this type lifts a pair of cotter piecesfrom a retainer to open the pair of cotter pieces, and inserts a valvestem between the pair of cotter pieces. The apparatus then engages thecotter pieces with the engaging grooves of the valve stem, and returnsthe cotter pieces to the retainer, thereby assembling the retainer tothe valve stem. Japanese Patent Laid-Open No. 5-301133 discloses anapparatus that fits a retainer to a valve stem and then fits a pair ofcotter pieces prepared in a separated state to the valve stem.

In each of the apparatuses of Japanese Patent Laid-Open No. 10-61420,Japanese Patent No. 4033703 and Japanese Patent Laid-Open No.2012-241519, fine adjustment often needs to be performed on an apparatusbasis to place the pair of cotter pieces lifted from the retainer in thesame posture. Hence, time may be required until the start of the firstoperation of the apparatus. The apparatus of Japanese Patent Laid-OpenNo. 5-301133 is advantageous in placing the pair of cotter pieces in thesame posture because the pair of cotter pieces are set in the separatedstate in advance. However, since the retainer and the pair of cotterpieces are separately supplied to the valve stem, the number of stepsincreases, and the cycle time tends to be long.

SUMMARY OF INVENTION

It is an object of the present invention to shorten the cycle time inassembling a retainer to a valve stem.

According to an aspect of the present invention, there is provided anassembling apparatus that places a retainer on a valve spring providedto surround an upper end of a valve stem, comprising:

an assembling head configured to place the retainer on the valve spring;and

a moving unit configured to move the assembling head between a supplyposition of the retainer and an assembling position,

wherein the assembling head comprises:

a holding unit configured to hold the retainer at a lower end; and

a push unit configured to push out the retainer held by the holdingunit,

the moving unit comprises:

a horizontal moving unit configured to move the assembling head in ahorizontal direction; and

an elevating unit configured to raise/lower the assembling head, and

the push unit comprises:

a push member supported to be able to advance/retreat along an elevatingdirection of the assembling head by the elevating unit; and

a biasing member configured to bias the push member in an advancingdirection.

According to another aspect of the present invention, there is providedan assembling apparatus that assembles a retainer by engaging a pair ofcotter pieces with an upper end of a valve stem, comprising:

a first assembling head configured to place the retainer on a valvespring provided to surround the upper end of the valve stem and assemblethe retainer;

a first moving unit configured to move the first assembling head betweena supply position of the retainer and an assembling position;

a second assembling head configured to hold the pair of cotter piecesand engages the pair of cotter pieces with the upper end of the valvestem; and

a second moving unit configured to move the second assembling headbetween a supply position of the pair of cotter pieces and the valvestem,

wherein the first assembling head comprises:

a holding unit configured to hold the retainer at a lower end; and

a push unit configured to push out the retainer held by the holdingunit,

the first moving unit comprises:

a horizontal moving unit configured to move the first assembling head ina horizontal direction; and

an elevating unit configured to raise/lower the first assembling head,and

the push unit comprises:

a push member supported to be able to advance/retreat along an elevatingdirection of the first assembling head by the elevating unit; and

a biasing member configured to bias the push member in an advancingdirection.

According to still another aspect of the present invention, there isprovided an assembling method of placing, by an assembling head, aretainer on a valve spring provided to surround an upper end of a valvestem, wherein

the assembling head comprises:

a holding unit configured to hold the retainer at a lower end; and

a push unit configured to push out the retainer held by the holdingunit,

the assembling method comprises

a moving step of moving the assembling head between a supply position ofthe retainer and an assembling position,

the moving step comprises:

a horizontal moving step of moving the assembling head in a horizontaldirection; and

an elevating step of raising/lowering the assembling head, and

the elevating step comprises:

a lowering step of lower the assembling head that holds the retainer;

a lowering stop step of stopping lowering of the assembling head beforethe retainer is placed on the valve spring;

a holding cancel step of starting cancel of holding of the retainer bythe holding unit and raising of the assembling head; and

a placement step of causing the push unit to push out the retainer heldby the holding unit and placing the retainer on the valve spring.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of an assembling apparatus according to anembodiment of the present invention;

FIG. 2 is a block diagram of the control unit of the assemblingapparatus shown in FIG. 1;

FIG. 3 is an explanatory view of a support device;

FIG. 4 is an explanatory view of a valve support unit;

FIG. 5 is an explanatory view of a cotter supplier;

FIG. 6 is an explanatory view of the cotter supplier;

FIG. 7 is an explanatory view of a cotter piece preparation unit;

FIG. 8 is an explanatory view of the cotter piece preparation unit;

FIG. 9 is an explanatory view of a retainer supplier;

FIG. 10 is an explanatory view of an assembling operation;

FIG. 11 is an explanatory view of the assembling operation;

FIG. 12 is an explanatory view of a retainer assembling head;

FIG. 13 is an explanatory view of the retainer assembling head;

FIG. 14 is an explanatory view of the retainer assembling head;

FIG. 15 is an explanatory view of the retainer assembling operation;

FIG. 16 is an explanatory view of a cotter assembling head;

FIG. 17 is an explanatory view of the cotter assembling head;

FIG. 18 is an explanatory view of a separating member and the drivingunit thereof;

FIG. 19 is an explanatory view of a storage member;

FIG. 20 is an explanatory view of the storage member;

FIG. 21 is an explanatory view of the storage member;

FIG. 22 is an explanatory view of the storage member;

FIG. 23 is an explanatory view of the cotter assembling head;

FIG. 24 is an explanatory view of the cotter assembling head; and

FIG. 25 is an explanatory view of the cotter assembling head.

DESCRIPTION OF EMBODIMENTS

<Outline of Apparatus>

An assembling apparatus A according to an embodiment of the presentinvention will be described with reference to the accompanying drawings.Note that in the drawings, arrows X and Y represent horizontaldirections orthogonal to each other, and an arrow Z represents avertical direction. FIG. 1 is a plan view schematically showing theassembling apparatus A. The assembling apparatus A is an apparatus thatassembles a retainer to a valve of a cylinder head 100 via a pair ofcotter pieces. The number of cylinders, the cylinder arrangement, andthe number of valves of the cylinder head 100 are not limited. Thecylinder head 100 according to this embodiment exemplarily includesthree cylinders arranged in a straight line and 12 valves (four valvesper cylinder).

The assembling apparatus A includes a conveying unit 1, a support device2, a cotter supplier 3, a retainer supplier 4, a moving unit 5, aplurality of retainer assembling heads 6, and a plurality of cotterassembling heads 7.

The conveying unit 1 conveys the cylinder head 100. The cylinder head100 is placed on a palette 160 and conveyed. In this embodiment, theconveying unit 1 includes two conveyor units 10. Each conveyor unit 10is, for example, a roller conveyor and extends in the X direction. Theconveying unit 1 forms a conveying line in the X direction. The palette160 is placed across the two conveyor units 10, and the cylinder head100 is conveyed in the X direction.

The support device 2 lifts up the cylinder head 100 from the conveyorunits 10 and supports the cylinder head 100 during an assemblingoperation. Details will be described later.

The cotter supplier 3 is a mechanism that supplies a pair of cotterpieces to each cotter assembling head 7. The retainer supplier 4 is amechanism that supplies a retainer to each assembling head 6. In thisembodiment, the retainer supplier 4 is arranged on one side (the rightside in FIG. 1) of the conveying line of the conveying unit 1 in the Ydirection, and the cotter supplier 3 is arranged on the other side (theleft side in FIG. 1) in the Y direction. This makes it possible toperform assembly of the retainer and the assembly of the pair of cotterpieces alternately from one side and the other side of the cylinder head100 or at overlapping timings without causing interference, therebyimproving the tact time.

The moving unit 5 is a device that independently moves the plurality ofretainer assembling heads 6 and the plurality of cotter assembling heads7. In this embodiment, the moving unit 5 is a gantry-type mechanism, andforms a unit that moves the plurality of retainer assembling heads 6 anda unit that moves the plurality of cotter assembling heads 7, whichshare some components.

The moving unit 5 includes a horizontal moving unit 50 and elevatingunits 55 a and 55 b. The horizontal moving unit 50 includes a pair ofrails 51 that are spaced apart in the X direction and arranged inparallel. Each rail 51 extends in the Y direction. The rails 51 areshared by the unit that moves the plurality of retainer assembling heads6 and the unit that moves the plurality of cotter assembling heads 7.However, the rails 51 may individually be provided.

Each rail 51 is provided with two sliders 52 a and 52 b capable ofindependently moving. The sliders 52 a and 52 b engage with the rails 51and can move along the rails 51. A rail 53 a is provided between the twosliders 52 a. A rail 53 b is provided between the two sliders 52 b. Therails 53 a and 53 b extend in the X direction.

A slider 54 a is provided on the rail 53 a. The slider 54 a engages withrail 53 a and can move along the rail 53 a. Similarly, a slider 54 b isprovided on the rail 53 b. The slider 54 b engages with rail 53 b andcan move along the rail 53 b.

The horizontal moving unit 50 includes a driving mechanism (not shown)that moves the sliders 52 a, 52 b, 54 a, and 54 b. The driving mechanismincludes, for example, a driving source such as a motor and a drivingforce transmission mechanism such as a ball screw mechanism.

The elevating unit 55 a is provided for the slider 54 a, and theelevating unit 55 b is provided for the slider 54 b. As shown in FIG. 5,each of the elevating units 55 a and 55 b includes a main body 551 fixedto a corresponding one of the sliders 54 a and 54 b, an elevating member552 to be raised/lowered in the Z direction, and a head support member553. The main body 551 is provided with a driving mechanism (forexample, a driving source such as a motor and a driving forcetransmission mechanism such as a ball screw mechanism) that moves theelevating member 552 in the Z direction

The head support member 553 is fixed to the lower end of the elevatingmember 552. The head support member 553 of the elevating unit 55 a isprovided with the plurality of retainer assembling heads 6. In thisembodiment, three retainer assembling heads 6 are arranged in a line inthe X direction. The head support member 553 of the elevating unit 55 bis provided with the plurality of cotter assembling heads 7. In thisembodiment, six cotter assembling heads 7 are provided. The six cotterassembling heads 7 are arranged in two lines in the Y direction. In eachline, three cotter assembling heads 7 are arranged in a line in the Xdirection.

With the above arrangement, all retainer assembling heads 6 are moved inthe horizontal direction (the X and Y directions) by the two sliders 52a, the rail 53 a, and the slider 54 a, and moved in the Z direction bythe elevating unit 55 a. All cotter assembling heads 7 are moved in thehorizontal direction (the X and Y directions) by the two sliders 52 b,the rail 53 b, and the slider 54 b, and moved in the Z direction by theelevating unit 55 b.

Each retainer assembling head 6 places a retainer supplied by theretainer supplier 4 on a valve spring. Each cotter assembling head 7engages a pair of cotter pieces with the upper end of a valve stem toassemble the retainer. Details will be described later.

<Control Unit>

The arrangement of a control unit 8 of the assembling apparatus A willbe described next with reference to FIG. 2. FIG. 2 is a block diagram ofthe control unit 8. The control unit 8 includes a processing unit 81, astorage unit 82, and an interface unit 83, which are connected to eachother via a bus (not shown). The processing unit 81 executes a programstored in the storage unit 82. The processing unit 81 is, for example, aCPU. The storage unit 82 is, for example, a RAM, a ROM, or a hard disk.The interface unit 83 is provided between the processing unit 81 andexternal devices (a host computer, a sensor 85, and an actuator 84). Theinterface unit 83 is, for example, a communication interface or an I/Ointerface. The host computer is a control apparatus that controls thewhole production facility in which the assembling apparatus A isprovided.

The actuator 84 is, for example, a motor or a solenoid included in theassembling apparatus A. The sensor 85 is, for example, a sensor thatdetects the operations of various movable bodies included in theassembling apparatus A.

Details of each component of the assembling apparatus A and an operationunder the control of the control unit 8 will be described below.

<Support Device>

The support device 2 supports the cylinder head 100 during theassembling operation. FIG. 3 is an explanatory view of the arrangementand operation of the support device 2. The support device 2 includes atable 20. A plurality of positioning pins 21 and a valve support unit 22are fixed on the table 20. The table 20 is supported by a pivot unit 24.The pivot unit (tilt unit) 24 is a device that supports the table 20pivotally about an axis parallel to the X direction and includes adriving mechanism (not shown) that makes the table 20 pivot. The drivingmechanism can be formed from, for example, a driving source such as amotor and a gear mechanism (for example, a worm gear mechanism).

The pivot unit 24 is supported by an elevating unit 25. The elevatingunit 25 includes, for example, an actuator such as an electric cylinderor an air cylinder, and raises/lowers the pivot unit 24 in the Zdirection.

The operation of the support device 2 will be described. Referring toFIG. 3, a state ST1 shows a standby state before the assemblingoperation. The table 20 and the pivot unit 24 are located at positionslower than the conveying surfaces of the conveyor units 10.

The cylinder head 100 to which the valve stems and valve springs 140 ofvalves 110 are assembled is conveyed above the support device 2 by theconveyor units 10 and stopped.

As shown in FIG. 14 and the like, the valve 110 includes a valve stem112 and a valve head 111 provided at the lower end of the valve stem112. A spring sheet 150 to be mounted on the cylinder head 100 and thevalve spring 140 are set on the valve stem 112. The valve spring 140 isprovided on the spring sheet 150 while surrounding the upper end of thevalve stem 112. As shown in FIG. 25 and the like, an engaging portion114 to be engaged with a pair of cotter pieces 120 is formed at an upperend 113 of the valve stem 112. The assembling apparatus A finallyassembles a retainer 130 to the upper end 113 via the pair of cotterpieces 120.

Referring back to FIG. 3, the elevating unit 25 is driven to raise thetable 20 and the pivot unit 24, as indicated by a state ST2. In theprocess of raising of the table 20, the plurality of positioning pins 21engage with the palette 160, and the cylinder head 100 is lifted up fromthe conveyor units 10 together with the palette 160. The operation ofassembling the retainer and the pair of cotter pieces is performed in astate in which the cylinder head 100 is thus lifted up from the conveyorunits 10. The valve support unit 22 abuts against the valves 110 toprevent the valves 110 from dropping off to the combustion chamber sideduring the assembling operation and also manage the positions of thevalves 110 during the assembling operation. Details will be describedlater.

Normally, the valve 110 on the intake side and the valve 110 on theexhaust side are not parallel to each other. In this embodiment, theoperation of assembling the retainer 130 and the pair of cotter pieces120 is performed in a state in which the valve stem of the valve 110 isparallel to the Z direction (the valve stem is directed verticallyupward). Hence, the table 20 is made to pivot (tilted) by the pivot unit24, as indicated by a state ST3. By the pivotal movement, for example,the valves 110 on the intake side are first set parallel to the Zdirection. When the assembling operation for the valves 110 on theintake side is completed, the valves 110 on the exhaust side are setparallel to the Z direction.

FIG. 4 shows a perspective view and a sectional view of the valvesupport unit 22. The valve support unit 22 is a device that abutsagainst the valve heads 111 provided at the lower ends of the valvestems 112 and presses the valve stems 112 upward while permitting thedownward movement of the valve stems 112 during the assemblingoperation. The valve support unit 22 includes a plurality of abuttingmembers 221.

The abutting member 221 is provided for each valve 110. Hence, in thisembodiment, there are 12 abutting members 221. The abutting member 221includes a plate-shaped abutting portion 221 a that abuts against thevalve head 111, and a shaft portion 221 b extending from the center ofthe abutting portion 221 a.

The valve support unit 22 also includes a support member 222 thatmovably supports the abutting members 221. The support member 222includes, for each abutting member 221, a hole 222 a in which the shaftportion 221 b is inserted. The abutting member 221 is supported to bemovable in the axial direction of the shaft portion 221 b. As indicatedby the state ST2 or state ST3 in FIG. 3, when the support device 2 issupporting the cylinder head 100, the shaft portion 221 b is locatedcoaxially with the valve stem 112.

An elastic member 223 is provided between each abutting portion 221 aand the support member 222. In this embodiment, the elastic member 223is a coil spring. The elastic member 223 is provided for each abuttingportion 221 a and surrounds the shaft portion 221 b. The elastic member223 biases the abutting member 221 to the side of the valve 110. Thatis, the elastic member 223 biases the valve 110 upward (to the closingdirection). This absorbs and relaxes a downward force acting on thevalve 110 while allowing the valve 110 to move downward.

The valve support unit 22 is provided with two sets of sensors 23 a and23 b configured to detect the downward moving amount of the valve stems112. In this embodiment, the two sets of sensors 23 a and 23 b areprovided on the support member 222. However, they may be provided onanother portion.

In this embodiment, the sensors 23 a and 23 b form a photosensor unit inwhich one sensor is a light-emitting element, and the other is alight-receiving element, and the optical axis of the light-emittingelement is a detection position P. If an object exists on the detectionposition P, light from the light-emitting element does not reach thelight-receiving element, and the presence of the object is detected.

One set of sensors 23 a and 23 b is provided for each line of theabutting members 221, in other words, on each of the intake side and theexhaust side of the valves 110. Hence, one set of sensors 23 a and 23 bmonitor the positions of the six abutting members 221.

The detection position P is set at a position between the abuttingportion 221 a and the support member 222 in the initial state. If thevalve 110 moves downward to move the abutting member 221 downward, theabutting portion 221 a is located on the detection position P, and thesensors 23 a and 23 b detect it. The detection position P is set suchthat the sensors 23 a and 23 b detect the movement of the valve 110 whenit moves downward by a predetermined amount. The detection result of thesensors 23 a and 23 b is used in the assembling operation by the cotterassembling heads 7.

Note that although a photosensor unit is used in this embodiment,another sensor (for example, a mechanical sensor) may be used. Thesensor may be provided for each abutting member 221 (for each valve110).

<Cotter Supplier>

The cotter supplier 3 will be described with reference to FIGS. 5 to 8.FIGS. 5 and 6 are elevation views showing the cotter supplier 3, thecotter assembling heads 7, and the moving unit 5 concerning the movementof the cotter assembling heads 7. FIG. 7 is an exploded perspective viewof a part of a preparation unit 30 of the cotter supplier 3, and FIG. 8is a sectional view of a part of the preparation unit 30.

The cotter supplier 3 includes the preparation unit 30 and a supply unit38. The preparation unit 30 is a device that prepares the pair of cotterpieces 120 in a separated state with a gap capable of passing the upperend 113 of the valve stem 112. The supply unit 38 is a unit that loadsthe pair of cotter pieces 120 on the preparation unit 30.

The preparation unit 30 includes a moving body 31. The moving body 31 isengaged with a rail 3 a extending in the X direction and guided, and canbe moved in the X direction by a driving mechanism (not shown). Thedriving mechanism is, for example, a ball screw mechanism or arack-and-pinion mechanism using a motor as a driving source. When themoving body 31 moves, the preparation unit 30 moves between a receivingposition to receive supply of the pair of cotter pieces 120 from thesupply unit 38 and a discharge position to supply the pair of cotterpieces 120 to the cotter assembling head 7. The receiving position isthe position indicated by a state ST12 or state ST13 in FIG. 5. Thedischarge position is the position indicated by states ST14 to ST16 inFIG. 6.

A plurality of storages 32 each configured to store the pair of cotterpieces 120 are mounted on the moving body 31. In this embodiment, threestorages 32 are provided in the X direction, and the arrangement of thestorages 32 corresponds to the arrangement of the cotter assemblingheads 7 in the X direction.

A plurality of driving pins 35 and a support plate 36 that supports theplurality of driving pins 35 are provided under the storages 32. Thedriving pin 35 is provided for each storage 32. The moving body is alsoprovided with a plurality of elevating units 37 configured toraise/lower the support plate 36.

Referring to FIGS. 6 and 7, the storage 32 is a tubular member. A pairof semicircular columnar storage holes 321 that store the pair of cotterpieces 120 in a separated state are formed in the top.

The storage 32 also has a shaft hole 322 formed in the Z direction andcommunicating with the storage holes 321. A lifting member 33 is storedin the shaft hole 322. A groove 332 is formed at the upper end of thelifting member 33. A pair of lifting portions 331 branched into twoparts are thus formed. Each lifting portion 331 is a columnar bodyhaving a semicircular section capable of entering the correspondingstorage hole 321.

An elastic member 34 is provided between the lifting member 33 and thestorage 32. In this embodiment, the elastic member 34 is a coil spring.The coil spring biases the lifting member 33 downward. When the liftingmember 33 is located on the lower side, the pair of cotter pieces 120can be inserted into the pair of storage holes 321.

The driving pin 35 is arranged coaxially with the lifting member 33.When the elevating units 37 are driven to raise the driving pins 35,each lifting member 33 is lifted up. Accordingly, the lifting member 33rises against the biasing of the elastic member 34, and the liftingportions 331 of the lifting member 33 lift up the pair of cotter pieces120 stored in the pair of storage holes 321.

An operation of loading the pair of cotter pieces 120 from the supplyunit 38 to the preparation unit 30 will be described with reference toFIG. 5. A state ST11 shows the initial state. The driving pins 35 arelocated at the lowering position. Hence, the lifting member 33 islocated on the lower side, as shown in FIG. 8, and the pair of storageholes 321 are in a state capable of storing the pair of cotter pieces120.

Next, the preparation unit 30 is moved to the receiving position. Inthis embodiment, the three storages 32 are sequentially made to face thesupply unit 38, and the pair of cotter pieces 120 is supplied. However,a plurality of supply units 38 may be provided to supply pairs of cotterpieces 120 to the plurality of storages 32 simultaneously.

The state ST12 shows a state in which one (the storage 32 at the rightend in FIG. 5) of the three storages 32 is made to face the supply unit38 to load the pair of cotter pieces 120 to the pair of storage holes321. The supply unit 38 drops or pushes out the pair of cotter pieces120 from above the storage 32, thereby loading the pair of cotter pieces120 to the pair of storage holes 321.

Subsequently, the preparation unit 30 is moved to store the pair ofcotter pieces 120 in another storage 32. The state ST13 shows a state inwhich another (the storage 32 at the center in FIG. 5) of the threestorages 32 is made to face the supply unit 38 to load the pair ofcotter pieces 120 to the pair of storage holes 321. The pairs of cotterpieces 120 are thus loaded to all storages 32.

With the above procedure, a plurality of sets of pairs of cotter pieces120 are prepared in the separated state. The operation then shifts to anoperation of discharging (supplying) the pairs of cotter pieces 120 tothe cotter assembling heads 7. This operation will be described withreference to FIG. 6.

First, the preparation unit 30 is moved to the discharge position(cotter supply position). The state ST14 shows a state in which thepreparation unit 30 moves to the discharge position. As for thepositional relationship, the three storages 32 and three cotterassembling heads 7 of the total of six cotter assembling heads 7 faceeach other in the Z direction.

Next, as shown in the state ST15, the elevating unit 55 b lowers thethree cotter assembling heads 7 to a position at which the pairs ofcotter pieces 120 can be received. Continuously, as shown in the stateST16, the elevating units 37 are driven to raise the driving pins 35 andlift up the lifting members 33. Accordingly, the three sets of pairs ofcotter pieces 120 stored in the three storages 32 are pushed out to thethree cotter assembling heads 7 while keeping the separated state. Thethree cotter assembling heads 7 hold the pushed pairs of cotter pieces120 in the separated state.

The pairs of cotter pieces 120 are thus supplied to the three cotterassembling heads 7. In this embodiment, since there are six cotterassembling heads 7, the operations shown in FIGS. 5 and 6 are repeatedtwice, thereby supplying the pairs of cotter pieces 120 to all the sixcotter assembling heads 7.

<Retainer Supplier>

The retainer supplier 4 will be described with reference to FIG. 9. FIG.9 shows a plan view of the retainer supplier 4 and an elevation view ofthe retainer assembling heads 6 and the moving unit 5 concerning themovement of the retainer assembling heads 6.

The retainer supplier 4 includes a preparation unit 40 and a supply unit43. The preparation unit 40 is a device configured to prepare theretainers 130 such that the retainer assembling heads 6 can hold them.The supply unit 43 is a unit configured to load the retainers 130 to thepreparation unit 40.

The preparation unit 40 includes a turntable 41 and a driving unit 42that rotates the turntable 41. The turntable 41 is a disc-shaped memberand can rotate about an axis parallel to the Z direction. A plurality ofplacement portions 411 are arranged on the turntable 41 at equal pitchesin the circumferential direction. In this embodiment, the placementportions 411 are concave portions on which the retainers 130 are placed.In FIG. 9, the placement portions 411 on which the retainers 130 areplaced are gray-colored, and the placement portions 411 on which theretainers 130 are not placed are open. The driving unit 42 is formedfrom, for example, a motor and a reduction gear.

A state ST21 indicates an operation of loading the retainer 130 from thesupply unit 43 to the preparation unit 40. The turntable 41 isintermittently rotated, and the supply unit 43 discharges and places theretainer 130 on the placement portion 411 located immediately under thesupply port. The retainers 130 are thus prepared on the placementportions 411.

An operation of extracting the retainer 130 by each retainer assemblinghead 6 will be described next. First, the retainer assembling heads 6are moved to the supply position to receive the supply of the retainer130. As for the positional relationship, the retainer assembling head 6that receives the supply of the retainer 130 first in the three retainerassembling heads 6 and a predetermined portion of the turntable 41 faceeach other in the Z direction. The rotation of the turntable 41 stops,the elevating unit 55 a lowers all the retainer assembling heads 6, asshown in a state ST22, and the retainer assembling head 6 that receivesthe supply of the retainer 130 first extracts the retainer 130 from theplacement portion 411.

Next, the elevating unit 55 a raises all the retainer assembling heads 6by a predetermined amount. After that, the turntable 41 is rotated tolocate the placement portion 411 with the retainer 130 at apredetermined portion, and after that, the retainer assembling head 6that receives the supply of the retainer 130 next is made to face apredetermined portion of the turntable 41. The elevating unit 55 alowers all the retainer assembling heads 6, as shown in a state ST23,and the retainer assembling head 6 that receives the supply of theretainer 130 next extracts the retainer 130 from the placement portion411. In this embodiment, since there are three retainer assembling heads6, the third retainer assembling head 6 also extracts the retainer 130in accordance with the same procedure as described above. The retainers130 are thus held by all the retainer assembling heads 6.

<Assembling Operation>

The assembling operation of the retainer 130 to the valve stem 112 willbe described with reference to FIGS. 10 and 11. To put it briefly, inthis embodiment, the retainer assembling head 6 places the retainer 130on the valve spring 140. After that, the cotter assembling head 7assembles the retainer 130 to the upper end 113 of the valve stem 112via the pair of cotter pieces 120.

A state ST31 shows a state in which all the retainer assembling heads 6hold the retainers 130, and all the cotter assembling heads 7 hold thepairs of cotter pieces 120 in the separated state. The cylinder head 100is supported on the support device 2 while putting the six valves 110 onone of the intake side and the exhaust side in a posture directed in theZ direction.

Next, as indicated by a state ST32, the moving unit 5 moves the retainerassembling heads 6 to an assembling position. This movement includes anoperation of horizontally moving the six retainer assembling heads 6onto the three valves 110 of the six valves 110 of the assemblingtarget, and an operation of lowering the three retainer assembling heads6 by the elevating unit 55 a and stopping them at a predeterminedposition. When the retainer assembling heads 6 are lowered and stoppedat the predetermined position, the retainers 130 are placed on the valvesprings 140, as will be described later in detail.

Next, as indicated by a state ST33, the moving unit 5 moves the retainerassembling heads 6 to the supply position to supply the new retainers130. In addition, the moving unit 5 moves the cotter assembling heads 7to the assembling position. This movement includes an operation ofhorizontally moving three cotter assembling heads 7 of the six cotterassembling heads 7 onto the three valves 110 on which the retainers 130are placed, and an operation of lowering the three cotter assemblingheads 7 by the elevating unit 55 b and stopping them at a predeterminedposition. When the cotter assembling heads 7 are lowered and stopped atthe predetermined position, the retainers 130 are assembled the valvestems 112 via the pairs of cotter pieces 120. The assembling operationfor the three valves 110 of the six valves 110 of the assembling targetis thus completed.

Next, the assembling operation of the retainers 130 to the remainingthree valves 110 of the six valves 110 of the assembling target isperformed. As indicated by a state ST34, the moving unit 5 temporarilyretracts the cotter assembling heads 7. The moving unit 5 moves theretainer assembling heads 6 that have received the supply of theretainers 130 to the assembling position. This movement includes anoperation of horizontally moving the three retainer assembling heads 6onto the remaining three valves 110 of the assembling target, and anoperation of lowering the three retainer assembling heads 6 by theelevating unit 55 b and stopping them at a predetermined position. Whenthe retainer assembling heads 6 are lowered and stopped at thepredetermined position, the retainers 130 are placed on the valvesprings 140.

Next, as indicated by a state ST35, the moving unit 5 moves the retainerassembling heads 6 to the supply position to supply the new retainers130 to the retainer assembling heads 6. In addition, the moving unit 5moves the cotter assembling heads 7 to the assembling position. Thismovement includes an operation of horizontally moving three cotterassembling heads 7 holding the pairs of cotter pieces 120 in the sixcotter assembling heads 7 onto the three valves 110 on which theretainers 130 are placed, and an operation of lowering the three cotterassembling heads 7 by the elevating unit 55 a and stopping them at apredetermined position. When the cotter assembling heads 7 are loweredand stopped at the predetermined position, the retainers 130 areassembled the valve stems 112 via the pairs of cotter pieces 120. Theassembling operation for the six valves 110 on one of the intake sideand the exhaust side is thus completed.

Next, the assembling operation for the six valves 110 on the other ofthe intake side and the exhaust side is started. As indicated by a stateST36, the pivot unit 24 makes the cylinder head 100 pivot, and puts thesix valves 110 on the other of the intake side and the exhaust side in aposture directed in the Z direction. In addition, each retainerassembling head 6 holds the retainer 130, and each cotter assemblinghead 7 holds the pair of cotter pieces 120. The same state as the stateST31 is thus obtained. The assembling operation for the six valves 110on the other of the intake side and the exhaust side is then performedin accordance with the above-described procedure.

<Retainer Assembling Head>

The retainer assembling head 6 will be described with reference to FIGS.12 to 15. The structure of the retainer assembling head 6 will bedescribed first with reference to FIG. 12. FIG. 12 is a sectional orcutaway view of a part of the retainer assembling head 6.

The retainer assembling head 6 includes a holding unit 60 that holds theretainer 130, and a push unit 63 that pushes out the retainer 130 heldby the holding unit 60. The holding unit 60 includes a plurality ofholding members 61, and a driving unit 62 that opens/closes theplurality of holding members 61. The push unit 63 includes a push member64, a support member 65 that supports the push member 64 such that itcan advance/retreat along the elevating direction of the retainerassembling head 6, that is, the Z direction, and a biasing unit 66.

In this embodiment, two holding members 61 are provided. However, threeor more holding members 61 may be provided. Each holding member 61 is anarm-shaped member extending in the Z direction. The two holding members61 are arranged in parallel so as to face each other in the Y direction.The two holding members 61 are provided around the push member 64, andthe push member 64 is located in the middle between the two holdingmembers 61 apart in the Y direction.

An abutting portion 611 that can abut against the peripheral portion ofthe retainer 130 is formed at the lower end of each holding member 61.The abutting portion 611 forms an L-shaped pawl and abuts against theside and lower surfaces of the flange portion of the retainer 130. Inother words, the flange portion of the retainer 130 is held by the twoabutting portions 611. A slit 612 is formed in the halfway portion ofeach holding members 61 so as to extend through the holding member 61 inthe Y direction. A detection piece 67 used to detect the position of thepush member 64 is inserted into the slit 612 of one holding member 61.

The driving unit 62 is an actuator configured to open/close the twoholding members 61. The two holding members 61 are translated indirections (Y direction) to come close or separate, as indicated byarrows. The driving unit 62 is formed by, for example, an air cylinder,an electric cylinder, or a ball screw mechanism or a rack-and-pinionmechanism using a motor as a driving source.

The push member 64 is a columnar body extending in the Z direction, andhas an engaging portion 641 at the lower end. The engaging portion 641is a projecting portion to be loosely fitted in the hole at the centerof the retainer 130, and has a truncated conical shape here.

The support member 65 is a tubular body extending in the Z direction,and a shaft hole 651 extending in the Z direction is formed at thecenter of the support member 65. The push member 64 is inserted into theshaft hole 651, and its movement in the Z direction is guided. A storagechamber 652 communicating with the shaft hole 651 is formed in the upperportion of the push member 64. The biasing unit 66 is stored in thestorage chamber 652.

In this embodiment, the biasing unit 66 is an elastic member,particularly, a coil spring, and is arranged between the top portion ofthe support member 65 and the upper portion of the push member 64. Thebiasing unit 66 may include a driving source. However, if an elasticmember is used, as in this embodiment, a simple structure can be formed.

The biasing unit 66 biases the push member 64 in the advancing direction(downward in the Z direction) in which the push member 64 comes out ofthe support member 65. As shown in FIG. 12, when located at thelowermost position, the push member 64 projects to the lower side of theabutting portions 611 at the lower ends of the holding members 61. Inother words, when located at the lowermost position, the push member 64projects to the lower side of the holding position of the retainer 130.

A slit 653 in which the detection piece 67 is inserted is formed in theperipheral wall of the storage chamber 652. The detection piece 67 is arod member (dog) extending in the horizontal direction (the Y directionin FIG. 12), and one end of the detection piece 67 is fixed to the upperportion of the push member 64.

The retainer assembling head 6 also includes a sensor 68 that detectsthe position of the push member 64. The sensor 68 is arranged by asensor support member 69 on a side of one holding member 61. The sensor68 is a proximity sensor that detects the approach/separation of the dog67. As the sensor 68, not only the proximity sensor but also atransmission photosensor can be applied. In this case, when thedetection piece 67 shields light between the light-emitting element andthe light-receiving element, the presence of the detection piece 67 isdetected.

The operation of the retainer assembling head 6 will be described withreference to FIGS. 13 to 15. FIG. 13 shows an operation (the operationin FIG. 9) of extracting the retainer 130 from the retainer supplier 4by the retainer assembling head 6.

A state ST41 shows a state in which the retainer assembling head 6 islocated on a predetermined position of the turntable 41. The two holdingmembers 61 are located at open positions apart from each other.

When the elevating unit 55 a lowers the retainer assembling head 6, theengaging portion 641 of the push member 64 is inserted into the hole atthe center of the retainer 130. When the retainer assembling head 6 isfurther lowered, the push member 64 is pushed into the support member 65against the biasing of the biasing unit 66.

When the retainer assembling head 6 is further lowered to push the pushmember 64 into the support member 65, and the detection piece 67 reachesthe position at which it is detected by the sensor 68, as indicated by astate ST42, the sensor 68 detects the detection piece 67, and thelowering of the retainer assembling head 6 is stopped.

When the detection piece 67 is detected by the sensor 68, the drivingunit 62 moves the two holding members 61 to close positions close toeach other, as indicated by a state ST43, and the abutting portions 611abut against the retainer 130. When the elevating unit 55 a raises theretainer assembling head 6, the retainer 130 is extracted from theplacement portion 411. The biasing unit 66 contracts in the Z direction.By the elastic force, a force to move (project) downward continuouslyacts on the push member 64. However, the force to project is restrictedwhen the abutting portions 611 of the holding members 61 hold the flangeportion of the retainer 130. The retainer 130 is thus held at the lowerend of the retainer assembling head 6. Accordingly, the extractionoperation of the retainer 130 is completed.

FIG. 14 shows an operation (the operation of the state ST32 in FIG. 10and the operation of the state ST34 in FIG. 11) of placing the retainer130 on the valve spring 140 by the retainer assembling head 6.

A state ST51 shows a state in which the retainer assembling head 6 islocated above the assembling position. The push member 64 and the valvestem 112 are located coaxially. As indicated by a state ST52, theretainer assembling head 6 is lowered by the elevating unit 55 a to theassembling position and stopped. The elevating height of the retainerassembling head 6 is detected by a sensor (for example, a sensor thatdetects the position of the elevating member 552) provided in theelevating unit 55 a.

Next, as shown in a state ST53, the driving unit 62 moves the twoholding members 61 to the open positions apart from each other to cancelthe holding of the retainer 130. Accordingly, the elastic force of thebiasing unit 66 makes the push member 64 project downward, and theretainer 130 is pushed to the side of the valve spring 140. At thistime, the engaging portion 641 of the push member 64 is kept inserted inthe hole at the center of the retainer 130, and the holding of theretainer 130 is maintained.

The holding of the retainer 130 is canceled, and at the same time, theelevating unit 55 a raises the retainer assembling head 6 from or theassembling position. At this time, although the retainer assembling head6 is raised, the push member 64 is moved downward by the elastic forceof the biasing unit 66. For this reason, the retainer 130 is pushed tothe side of the valve spring 140 and placed on the valve spring 140. Atthis time, a part of the upper end 113 of the valve stem 112 is insertedinto the hole at the center of the retainer 130, and the retainer 130 isthus prevented from dropping from the valve spring 140.

In this embodiment, since the push member 64 can push out the retainer130, the assembling position (stop position) in the state ST52 can be aposition higher than the position where the retainer 130 is placed onthe valve spring 140. FIG. 15 is an explanatory view of this. The stateST52 of FIG. 15 shows an enlarged view of the periphery of the retainer130 in the state ST52 of FIG. 14. A state ST55 of FIG. 15 shows a statein which the assembly of the retainer 130 (the placement of the retainer130 on the valve spring 140) is completed.

As shown in the state ST52 of FIG. 15, the assembling position where thelowering of the retainer assembling head 6 is stopped is set such thatthe lower surface of the flange portion of the retainer 130 is set at aposition higher than the upper surface of the valve spring 140. In theexample of FIG. 15, the assembling position is set to a position higherthan the position of the retainer 130 after assembly by H. After that,as indicated by states ST53 and ST54 in FIG. 14, cancel of the holdingof the retainer 130 and raising of the retainer assembling head 6 arestarted. The cancel and raising may be done simultaneously.

As described above, before the retainer 130 is placed on the valvespring 140, the retainer assembling head 6 stops lowering and startsrising. This can reduce the downward moving length and the upward movinglength of the retainer assembling head 6 and shorten the cycle time. Atthe stage of canceling the holding of the retainer 130, the valve spring140 is in a natural state (a state in which the biasing force does notact). It is therefore possible to prevent the retainer 130 from unstablybehaving when the retainer 130 is placed and receives the reaction ofthe valve spring 140. When the holding of the retainer 130 is canceled,the retainer 130 is sandwiched between the valve spring 140 and the pushmember 64. Hence, the retainer 130 is continuously prevented fromunstably behaving.

<Cotter Assembling Head>

The cotter assembling head 7 will be described with reference to FIGS.16 to 25. The entire structure of the cotter assembling head 7 will bedescribed first with reference to FIGS. 16 and 17. FIG. 16 is aperspective view of the cotter assembling head 7, and FIG. 17 is asectional or cutaway view of a part of the cotter assembling head 7.

The cotter assembling head 7 includes a holding unit 70 and a storagemember 78. The storage member 78 stores the pair of cotter pieces 120 inthe separated state. The holding unit 70 includes a mechanism capable ofholding the pair of cotter pieces 120 stored in the storage member 78 inthe separated state, and canceling the separated state and pressing thepair of cotter pieces 120 against the upper end 113 of the valve stem112. The structure of the holding unit 70 will be described first.

The holding unit 70 includes a holding base member 71, a support member72, and a pair of pressing members 75. The support member 72 is atubular body extending in the Z direction, and a shaft hole 721extending in the Z direction is formed at the center of the supportmember 72. A separating member 73 is inserted into the shaft hole 721,and the movement of the separating member 73 in the Z direction isguided by the shaft hole 721.

A storage chamber 723 communicating with the shaft hole 721 is formed inthe upper portion of the support member 72. An elastic member 744 isstored in the storage chamber 723. In this embodiment, the elasticmember 744 is a coil spring, and is arranged between the top portion ofthe support member 72 and a disc-shaped boss portion 733 provided in theupper portion of the separating member 73 to bias the separating member73 downward. The outer diameter of the boss portion 733 is larger thanthe outer diameter of the separating member 73.

A storage chamber 724 communicating with the shaft hole 721 is formed inthe lower portion of the support member 72. When the storage member 78is inserted into the storage chamber 724, the storage member 78 ispositioned and fixed relative to the storage chamber 724.

Grooves 722 are formed in both side portions of the support member 72from the center to the lower portion in the Y direction. The pressingmembers 75 are arranged in the grooves 722. Each pressing member 75 isan arm-shaped member extending in the Z direction, and supported by ashaft 751 to be swingable with respect to the support member 72.

The lower end of each pressing member 75 includes a pressing portion 752bent inward. The end of the pressing portion 752 abuts against the outersurface of the cotter piece 120 and presses the cotter pieces 120. Anelastic member 76 is arranged between the inner surface at the upper endof each pressing member 75 and the side wall of the support member 72.The elastic member 76 biases the inner surface at the upper end of thepressing member 75 outward in the radial direction. The pressingportions 752 are thus biased in the directions (close positiondirections) to come close to each other.

Support members (brackets) 77 a are attached to the support member 72,and actuators 77 are supported by the support members 77 a. Theactuators 77 are arranged at portions facing the upper ends of thepressing members 75. The actuator 77 is, for example, an electriccylinder or an air cylinder. Each actuator 77 is driven to press theupper end of the pressing member 75 to the side of the support member 72against the biasing of the elastic member 76, and the pressing portions752 are moved in the directions (open position directions) to separatefrom each other. In this embodiment, the actuator 77 is provided foreach pressing member 75. However, one actuator may be shared by the twopressing members 75, and the driving force may be distributed to thepressing members 75 by a link mechanism.

The upper end of the support member 72 is fixed to the lower surfaceside of the holding base member 71, and a driving unit 74 configured toraise/lower the separating member 73 in the Z direction is supported onthe upper surface side of the holding base member 71. The separatingmember 73 and the driving unit 74 will be described with reference toFIG. 18 as well. FIG. 18 shows a perspective view of the separatingmember 73, a function explanatory view of the lower end of theseparating member 73, and an explanatory view of the structure of a partof the driving unit 74.

The driving unit 74 includes an actuator 741, a pair of links 742, andthe above-described elastic member 744.

The actuator 741 is, for example, an electric cylinder or an aircylinder. The rod portion of the actuator 741 advances/retreats in the Zdirection, and has, at its distal end, an engaging member 741 a having arectangular body shape.

The pair of links 742 extend in the Y direction through a pair ofgrooves 725 provided near the upper end of the support member 72. Theends of the pair of links 742 are connected by shafts 743 a and 743 bprovided in parallel to the x-axis direction. The shaft 743 a isinserted into a hole (not shown) formed in a bracket 711 suspended onthe lower surface side of the holding base member 71, and the positionof the shaft 743 a does not change. The shaft 743 b is inserted into along hole (not shown) formed in the engaging member 741 a. An abuttingportion 742 a projecting upward is formed at the center of each link742.

When the rod portion of the actuator 741 is retreated (moved upward inFIG. 17), the engaging member 741 a rises, and the shaft 743 b insertedinto the engaging member 741 a rises, as indicated by an arrow in FIG.18. Since the position of the shaft 743 a is fixed, the pair of links742 pivot about the shaft 743 a (counterclockwise in FIG. 17), and theabutting portions 742 a abut against the lower surface of the bossportion 733 and raise the boss portion 733. Accordingly, the separatingmember 73 integrally connected to the boss portion 733 is raised upward.When the rod portion of the actuator 741 is retreated, the separatingmember 73 is moved upward against the biasing of the elastic member 744.When the driving of the actuator 741 is stopped, the separating member73 is moved downward by the biasing of the elastic member 744.

The separating member 73 is a columnar member extending in the Zdirection. As shown in FIG. 18, a slit-shaped opening portion 732opening downward and capable of receiving the upper end 113 of the valvestem 112 is formed at the lower end of the separating member 73. Thelower end of the separating member 73 thus forms a pair of spacerportions 731 branched into two parts. Each spacer portion 731 canintervene between the pair of cotter pieces 120 supplied in theseparated state from the cotter supplier 3 and maintain the pair ofcotter pieces 120 in the separated state. When the separating member 73is moved upward by the driving unit 74 to retreat the spacer portions731 from the pair of cotter pieces 120, the separated state of the pairof cotter pieces 120 is canceled. The separating member 73 and thedriving unit 74 thus constitute a shutter mechanism that switchesbetween a state in which the spacer portions 731 intervene between thepair of cotter pieces 120 and a state in which the separation of thepair of cotter pieces 120 is canceled.

The structure and function of the storage member 78 will be describedwith reference to FIGS. 19 to 21. First, the structure of the storagemember 78 will be described with reference to FIGS. 19 and 20. FIG. 19shows two perspective views of the storage member 78 viewed from theupper side and lower side, and FIG. 20 is a sectional view taken along aline I-I in FIG. 19.

The storage member 78 includes an upper wall portion 781 and side wallportions (peripheral wall portions) 782 and 783, and has an internalstorage chamber 780 defined by the wall portions. The storage chamber780 is a space whose lower side is opened by an opening 780 c, andincludes an upper storage portion 780 b defined by the upper wallportion 781 and the side wall portion 782, and a lower storage portion780 a defined by the side wall portion 783.

The storage portion 780 a is a space to store the pair of cotter pieces120. The pair of cotter pieces 120 supplied in the separated state fromthe cotter supplier 3 are inserted into the storage portion 780 a fromthe lower side. The storage portion 780 b is a space to store the upperportion of the upper end 113 of the valve stem 112. The upper end 113 ofthe valve stem 112 is also inserted into the storage portions 780 a and780 b from the lower side.

The storage portion 780 a and the storage portion 780 b are providedcontinuously in the vertical direction. The storage portion 780 b has analmost elliptical cross-sectional shape, and the storage portion 780 ahas an almost circular cross-sectional shape. The storage portion 780 bis provided to have a sectional area smaller than that of the storageportion 780 a.

A pair of holes 781 b extending through in the Z direction are formed inthe upper wall portion 781. The holes 781 b are formed into a size andshape that allow the pair of spacer portions 731 of the separatingmember 73 to be inserted. When the separating member 73 is moved by thedriving unit 74 in the Z direction (insertion/removal direction)relative to the storage member 78, the pair of spacer portions 731 ofthe separating member 73 can be inserted/removed into/from the center ofthe storage chamber 780 from above the storage member 78.

The inner wall of the storage chamber 780 includes an upper wall 781 athat is the lower surface of the upper wall portion 781, side walls 782a and 783 a that are the inner surfaces of the side wall portions 782and 783, and a horizontal step portion 784 that is the boundary betweenthe storage portion 780 a and the storage portion 780 b. The side walls782 a and 783 a are uneven in conformity with the outer surfaces of thespacer portions 731 and the pair of cotter pieces 120.

Grooves 782 b with closed bottoms are formed in the side wall portion782 on both sides in the Y direction. The pressing members 75 areinserted into the grooves 782 b from the sides, and interference of thepressing members 75 is avoided. Grooves 783 b communicating with thestorage portion 780 a are formed in the side wall portion 783 on bothsides in the Y direction. The grooves 783 b allow the pressing portions752 of the pressing members 75 to enter the storage portion 780 a. Thatis, by the opening/closing operation of the pressing portions 752 by thepivotal movement of the storage member 78, the pressing portions 752 canenter the storage chamber 780 from both sides of the storage member 78or retreat.

An abutting portion 785 a that abuts against the upper surface of theretainer 130 is formed on a bottom portion 785 of the storage member 78.The abutting portion 785 a is formed into a truncated conical shapeconforming to the shape of the upper surface of the retainer 130 so asto surround the opening 780 c.

The storage form of the pair of cotter pieces 120 or the upper end 113of the valve stem 112 in the storage chamber 780 will be described withreference to FIG. 21. A state ST61 shows a state in which the pair ofcotter pieces 120 in the separated state are stored in the storageportion 780 a. The upper end faces of the pair of cotter pieces 120inserted into the storage chamber 780 and stored in the storage portion(cotter storage portion) 780 a abut against the step portion 784. TheZ-direction absolute position of the pair of cotter pieces 120 relativeto the storage member 78 is thus determined. The step portion 784 issometimes called an abutting portion 784, or a first positioningreference portion or first positioning reference surface.

A state ST62 shows a state in which the pair of cotter pieces 120 in theseparated state are stored in the storage portion 780 a, and the upperend 113 of the valve stem 112 is stored in the storage portion 780 b. Anupper end face 115 of the valve stem 112 inserted into the storagechamber 780 and stored in the storage portion (valve stem storageportion) 780 b abuts against the upper wall 781 a. The Z-directionabsolute position of the valve stem 112 relative to the storage member78 is thus determined. As a result, the Z-direction absolute positionsof the pair of cotter pieces 120 and the valve stem 112 relative to thestorage member 78 are determined, and the relative positionalrelationship between the pair of cotter pieces 120 and the valve stem112 is uniquely determined. The upper wall 781 a is sometimes called anabutting portion 781 a, or a second positioning reference portion orsecond positioning reference surface.

A state ST63 shows a state in which the pair of cotter pieces 120 areclosed from the state ST62 to abut their end faces and engage them withthe engaging portion 114 of the valve stem 112. In this embodiment, theengaging portion 114 has a plurality of protrusions, and the pair ofcotter pieces 120 have a plurality of groove portions to be engaged withthe protrusions.

In this embodiment, the valve stem 112 and the pair of cotter pieces 120are physically and mechanically positioned to each other in the Zdirection using the storage member 78 as a reference. When the distancebetween the abutting portion 781 a and the abutting portion 784 isdesigned based on the distance from the upper end face 115 of the valvestem 112 to the engaging portion 114, theoretically, the valve stem 112and the pair of cotter pieces 120 are always positioned in the Zdirection. In other words, the relative positional relationship betweenthe valve stem 112 and the pair of cotter pieces 120 is uniquelydetermined by the design/manufacturing accuracy of the storage member 78and the separating member 73. Hence, when engaging the pair of cotterpieces 120 with the valve stem 112, a position shift never occurs.Particularly, if the engaging portion 114 has the plurality ofprotrusions, and the pair of cotter pieces 120 has the plurality ofgroove portions, higher positioning accuracy is required. In thisembodiment, it is possible to cope with the requirement of positioningaccuracy.

FIG. 22 shows a cutaway perspective view of the peripheral structure ofthe storage member 78 and a sectional view taken along a line II-II atthe time of assembling operation corresponding to the state ST62. In thecutaway perspective view, one of the pair of pressing members 75 is notillustrated.

The pair of cotter pieces 120 are stored between the spacer portions 731and the inner wall of the storage chamber 780. The pair of cotter pieces120 are biased toward the center of the storage chamber 780 by thepressing portions 752 of the pressing member 75. However, the spacerportions 731 intervene between the pair of cotter pieces 120. Hence, asindicated by the state ST63 in FIG. 21, the pair of cotter pieces 120are not closed, and the separated state with a gap capable of receivingthe upper end 113 of the valve stem 112 is maintained. In addition, thepair of cotter pieces 120 are clamped by the pair of spacer portions 731and the pressing portions 752 and held by the cotter assembling head 7.In other words, the pressing portions 752 bias the outer surfaces of thepair of cotter pieces 120 toward the center of the storage chamber 780,that is, the pair of spacer portions 731, and in this state, the pair ofcotter pieces 120 are held by the cotter assembling head 7.

The operation of the cotter assembling head 7 will be described withreference to FIGS. 23 to 25. FIG. 23 shows an operation (the operationshown in FIGS. 5 and 6) of receiving the supply of the pair of cotterpieces 120 from the cotter supplier 3 by the cotter assembling head 7.

A state ST71 shows a state in which the supply unit 38 loads the pair ofcotter pieces 120 to the pair of storage holes 321 of the storage 32. Astate ST72 shows a state in which the storage 32 and the cotterassembling head 7 face each other in the Z direction. When the actuators77 are driven, the pressing members 75 pivot to the open positions. Theseparating member 73 is located at the lowering position.

The elevating unit 55 b lowers the cotter assembling head 7 to abut theopening 780 c of the storage member 78 against the upper surface of thestorage 32, and at the same time, the lifting member 33 is lifted up byan elevating unit (not shown), as indicated by a state ST73.Accordingly, the pair of cotter pieces 120 enter the storage portion 780a from below the storage chamber 780 and abut against the abuttingportion 784, and are thus positioned in the Z direction. In addition,since the pair of spacer portions 731 intervene between the pair ofcotter pieces 120, the pair of cotter pieces 120 are prevented fromcoming close to each other.

As indicated by a state ST74, biasing by the actuator 77 stops, and theelastic members 76 apply a biasing force to make the pressing members 75pivot to the close positions. The pair of cotter pieces 120 are clampedbetween the pressing portions 752 and the spacer portions 731 and heldby the cotter assembling head 7. The extraction (pickup) operation ofthe pair of cotter pieces 120 is thus completed.

FIGS. 24 and 25 show an operation (the operation of the state ST33 inFIG. 10 and the state ST35 in FIG. 11) of assembling the retainer 130 tothe valve stem 112 via the pair of cotter pieces 120 by the cotterassembling head 7.

A state ST81 shows a state in which the cotter assembling head 7 islocated above the assembling position. The separating member 73 and thevalve stem 112 are located coaxially. The retainer 130 is placed on thevalve spring 140 in the previous step (the state ST55 in FIG. 15).

As shown in a state ST82, the cotter assembling head 7 is lowered by theelevating unit 55 b to the assembling position and stopped. In thisprocess, the abutting portion 785 a of the storage member 78 abutsagainst the upper surface of the retainer 130. Simultaneously, theretainer 130 is pushed down to the valve stem 112, and the valve spring140 is compressed. In addition, when the upper end 113 of the valve stem112 enters the opening portion 732 between the spacer portions 731, andthe upper end face 115 abuts against the abutting portion 781 a, thevalve stem 112 (valve 110) is pushed down.

When the valve 110 is pushed down, the abutting member 221 of the valvesupport unit 22 that biases the valve 110 upward is also pushed down.After that, when the arrival of the abutting member 221 at the detectionposition P is detected by the sensors 23 a and 23 b, the lowering of thecotter assembling head 7 is stopped.

A state ST83 shows the state on the periphery of the storage member 78when the lowering of the cotter assembling head 7 is stopped. The stateshown in FIG. 22 is obtained. The position of the valve stem 112 ismainly shown on the left side, and the position of the spacer portion731 is mainly shown on the right side. The spacer portions 731 intervenebetween the pair of cotter pieces 120, and the separated state with agap capable of receiving the upper end 113 of the valve stem 112 ismaintained. The upper end face 115 of the valve stem 112 abuts againstthe abutting portion 781 a halfway through the lowering of the cotterassembling head 7, and the valve stem 112 is positioned relative to thestorage member 78 in the Z direction. Positioning between the pair ofcotter pieces 120 and the engaging portion 114 of the valve stem 112 inthe Z direction is thus completed. The lowering stop position of thecotter assembling head 7 is set to a position where the upper end face115 of the valve stem 112 properly abuts against the abutting portion781 a.

Next, the actuator 741 is driven to raise the separating member 73, asindicated by a state ST84, and the pair of spacer portions 731 areretreated from the pair of cotter pieces 120. The pair of cotter pieces120 are biased toward the center of the storage chamber 780 by the pairof pressing portions 752. Hence, the separated state is canceled by theretreat of the spacer portions 731, and the pair of cotter pieces 120are pressed against the upper end 113 of the valve stem 112. The pair ofcotter pieces 120 are moved to the center of the storage chamber 780,and their end faces abut and close. Accordingly, a state in which thepair of cotter pieces 120 engage with the engaging portion 114, asindicated by a state ST85, is obtained.

Next, the elevating unit 55 b raises the cotter assembling head 7 fromthe assembling position. Even during the raising of the cotterassembling head 7, the pair of cotter pieces 120 are biased toward thecenter of the storage chamber 780 by the pair of pressing portions 752and therefore do not return to the separated state. When the cotterassembling head 7 is raised, the retainer 130 is also lifted up by theelastic restoring force of the valve spring 140, and the pair of cotterpieces 120 are inserted into the hole at the center of the retainer 130,as shown in a state ST86. The elastic restoring force of the valvespring 140 continuously acts even after that. However, the pair ofcotter pieces 120 prevent the retainer 130 from further rising, and theassembling operation of the retainer 130 to the valve stem 112 iscompleted.

According to the assembling method of this embodiment, the pair ofcotter pieces 120 are held in advance in the separated state andassembled to the valve stem 112. For this reason, a separation failureof the pair of cotter pieces 120 cannot occur. In addition, the pair ofcotter pieces 120 are oriented and positioned by the first positioningreference portion such that the posture of the cotter pieces 120relative to the storage member 78 of the cotter assembling head 7 is setin a predetermined state (completely separated state). The cotter pieces120 in the adjusted posture and position are held in this state andsupplied to the valve stem 112. The valve stem 112 is oriented andpositioned by the second positioning reference portion such that itsposition in the vertical direction relative to the storage member 78 ofthe cotter assembling head 7 is set to a predetermined position. As aresult, the relative positional relationship between the pair of cotterpieces 120 and the valve stem 112 in the vertical direction and in thehorizontal direction is uniquely determined.

Hence, according to the assembling method of this embodiment, the pairof cotter pieces 120 are supplied to the upper end 113 of the valve stem112 always in the same posture and the same positional relationship. Itis therefore possible to assemble the retainer 130 to the upper end 113of the valve stem 112 by the pair of cotter pieces 120 easily at highaccuracy without adjusting the apparatus, in other words, without muchtrial and error. In addition, since the assembling apparatus accordingto this embodiment is adjustment-free, the apparatus can quickly bestarted, resulting in a large effect of shortening the manufacturingperiod.

The present invention is not limited to the above embodiments, andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention, the following claims are made.

1. An assembling method of placing, by an assembling head, a retainer ona valve spring provided to surround an upper end of a valve stem,wherein the assembling head comprises: a holding unit configured to holdthe retainer at a lower end; and a push unit configured to push out theretainer held by the holding unit, wherein the assembling methodcomprises a moving step of moving the assembling head between a supplyposition of the retainer and an assembling position, wherein the movingstep comprises: a horizontal moving step of moving the assembling headin a horizontal direction; and an elevating step of raising/lowering theassembling head, and wherein the elevating step comprises: a loweringstep of lower the assembling head that holds the retainer; a loweringstop step of stopping lowering of the assembling head before theretainer is placed on the valve spring; a holding cancel step ofstarting cancel of holding of the retainer by the holding unit andraising of the assembling head; and a placement step of causing the pushunit to push out the retainer held by the holding unit and placing theretainer on the valve spring.
 2. The assembling method according toclaim 1, further comprising an extracting step of extracting theretainer from a retainer supplier, wherein the holding unit includes twoholding members which face each other in a direction orthogonal to anelevating direction of the assembling head in the elevating step, andwherein the extracting step comprises: a step of lowering the assemblinghead that does not hold the retainer in a state in which that the twoholding members are located at open positions apart from each other; astep of detecting a detection piece by a sensor; and a step of stoppinglowering of the assembling head that does not hold the retainer andmoving the two holding members to close positions close to each otherwhen the detection piece is detected by the sensor.
 3. The assemblingmethod according to claim 1, wherein the push unit includes a pushmember, and the method further comprises a step of detecting a positionof the push member by a sensor.
 4. The assembling method according toclaim 1, wherein the assembling head includes: two holding members whichface each other in a direction orthogonal to an elevating direction ofthe assembling head in the elevating step; and a driving unit whichopens/closes the two holding members in the direction orthogonal to theelevating direction, and the holding cancel step includes a step ofopening the two holding members by the driving unit so as to cancel theholding of the retainer by the holding unit.
 5. An assembling method ofassembling a retainer by engaging a pair of cotter pieces with an upperend of a valve stem, comprising: a first moving step of moving a firstassembling head, configured to perform assembling of the retainer,between a supply position of the retainer and an assembling position;and a second moving step of moving a second assembling head, configuredto hold the pair of cotter pieces and engaging the pair of cotter pieceswith the upper end of the valve stem, between the supply position of theretainer and the assembling position, wherein the first moving stepincludes a retainer placing step of placing the retainer which is heldby the first assembling head on a valve spring provided to surround theupper end of the valve stem, wherein the retainer placing step includes:a moving stop step of stopping moving of the first assembling head whichholds the retainer before the retainer is placed on the valve spring; aholding cancel step of canceling of holding of the retainer by the firstassembling unit; and a pushing out step of pushing out the retainer heldby the first assembling head so as to place the retainer on the valvespring, and wherein the second moving step includes an assembling stepof moving the pair of cotter pieces to a position of valve stem to whichthe retainer and the valve spring are set and assembling the retainer tothe valve stem with engaging the pair of cotter pieces with the valvestem.
 6. The assembling method according to claim 5, further comprising:a supplying step of supplying the retainer by a retainer supplier; and asupplying step of supplying the pair of cotter pieces by a cottersupplier.
 7. The assembling method according to claim 5, furthercomprising: a support step of supporting a cylinder head, which includesthe valve stem on which the retainer and the pair of cotter pieces arenot assembled, at a position during an assembling operation; and asupport canceling step of canceling of supporting of the cylinder headwhich includes the valve stem on which the retainer and the pair ofcotter pieces have been assembled.